diff --git a/composer.json b/composer.json
index 8c877ea..e8f1cbe 100644
--- a/composer.json
+++ b/composer.json
@@ -18,6 +18,7 @@
         "ext-simplexml": "*",
         "ecphp/cas-bundle": "^1",
         "ecphp/ecas": "^2",
+        "symfony/dependency-injection": "^4.4",
         "symfony/framework-bundle": "^4.4"
     },
     "require-dev": {
diff --git a/src/DependencyInjection/EuLoginExtension.php b/src/DependencyInjection/EuLoginExtension.php
index c0eddc8..2d850fe 100644
--- a/src/DependencyInjection/EuLoginExtension.php
+++ b/src/DependencyInjection/EuLoginExtension.php
@@ -6,7 +6,7 @@
 
 use Symfony\Component\Config\FileLocator;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
-use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;
+use Symfony\Component\DependencyInjection\Loader\PhpFileLoader;
 use Symfony\Component\HttpKernel\DependencyInjection\Extension;
 
 /**
@@ -21,7 +21,7 @@ class EuLoginExtension extends Extension
     public function load(array $configs, ContainerBuilder $container): void
     {
         // Load EU Login services.
-        $loader = new YamlFileLoader($container, new FileLocator(__DIR__ . '/../Resources/config'));
-        $loader->load('services.yaml');
+        $loader = new PhpFileLoader($container, new FileLocator(__DIR__ . '/../Resources/config'));
+        $loader->load('services.php');
     }
 }
diff --git a/src/Resources/config/services.php b/src/Resources/config/services.php
new file mode 100644
index 0000000..bda9aa8
--- /dev/null
+++ b/src/Resources/config/services.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Symfony\Component\DependencyInjection\Loader\Configurator;
+
+use EcPhp\Ecas\Ecas;
+use EcPhp\Ecas\EcasProperties;
+use EcPhp\EuLoginBundle\Security\Core\User\EuLoginUserProvider;
+
+return static function (ContainerConfigurator $container) {
+    $container
+        ->services()
+        ->set('eulogin.userprovider', EuLoginUserProvider::class);
+
+    $container
+        ->services()
+        ->set('ecas.configuration', EcasProperties::class)
+        ->decorate('cas.configuration')
+        ->args([
+            ref('ecas.configuration.inner'),
+            ref('request_stack'),
+        ]);
+
+    $container
+        ->services()
+        ->set('ecas', Ecas::class)
+        ->decorate('cas')
+        ->args([
+            ref('cas.inner'),
+            ref('nyholm.psr7.psr17_factory'),
+        ]);
+};
diff --git a/src/Resources/config/services.yaml b/src/Resources/config/services.yaml
deleted file mode 100644
index a0007ac..0000000
--- a/src/Resources/config/services.yaml
+++ /dev/null
@@ -1,13 +0,0 @@
-services:
-    eulogin.userprovider:
-        class: EcPhp\EuLoginBundle\Security\Core\User\EuLoginUserProvider
-
-    ecas.configuration:
-        class: EcPhp\Ecas\EcasProperties
-        decorates: 'cas.configuration'
-        arguments: ['@ecas.configuration.inner', '@request_stack']
-
-    ecas:
-        class: EcPhp\Ecas\Ecas
-        decorates: 'cas'
-        arguments: ['@ecas.inner', '@nyholm.psr7.psr17_factory']